Levels of aflatoxins in flour ingredients from micro, small and medium enterprises in Nairobi County and the effect on feeding rats

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Abstract

In Kenya, aflatoxicosis is a major public health concern and several outbreaks have occurred in the past due to the consumption of contaminated maize and maize products. Even when there are no reported cases of illness or deaths, it is believed that the consumer is constantly exposed to sub-lethal doses of the toxin above the established national maximum limit. The risk of developing liver cancer is six times higher in individuals exposed to aflatoxins. Epidemiological studies have also associated prolonged exposure of the mycotoxins with stunting and impaired growth in children due to protein malabsorption.
Much of the flours and flour mixes used for feeding especially children in Nairobi almost always contain maize and are usually purchased from small scale millers found widespread in the county. These millers do very little quality control if any.
This study was designed to assess the levels of aflatoxin contamination of flours from these small enterprises and its effect on growth when fed to rats. Questionnaires were administered to 107 Micro, Small and Medium Enterprises (MSMEs) to collect data on the nature, diversity and usage of milled flour products they supply. A total of 32 flour samples of maize, sorghum, finger millet and groundnut flours were collected from a selection of the interviewed MSMEs to test for levels of aflatoxin and to use to prepare contaminated rat pellets. Wistar rats were fed on the prepared pellets for a period of 21 days during which their weight, length and daily food consumption were recorded. Regression
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analysis was done to determine correlations between variables. After the 21 days, a post mortem was done on the rats and their livers extracted for histopathological examination.
The aflatoxin levels in the 32 flour samples ranged from 2,190.30 ppb – < 1 ppb. Three (3), 6 and 5 out of 8 of maize flour, sorghum and groundnuts samples respectively collected had aflatoxin levels above the Kenya Bureau of Standards maximum limit of 10 ppb. Groundnut flour had the highest mean aflatoxin level contamination at 304.51 ppb. The mean aflatoxin level in maize flour, sorghum and millet flours was 59.73 ppb, 39.21 ppb and 34.80 ppb respectively. Regression analysis showed a significant negative correlation between weight gain of rats and consumption of aflatoxin contaminated feed. Amount of food consumed was also negatively correlated to ingestion of aflatoxin contaminated feed. Increase in length was not significantly correlated to consumption of aflatoxins. The histopathological examination of the rat livers showed fatty degeneration, cell outline alteration, nuclear changes, all signs of liver cell injury and necrosis.
The study established that flour products supplied by MSMEs in Nairobi County are contaminated with aflatoxins and are possible causes of poor growth, liver damage and necrosis.